Electron Devices
Vacuum electronic devices employ a flow of electrons through a vacuum space between a cathode and an anode. Through manipulation of the voltages of intermediate electrodes, the use of magnetic fields, or other techniques, various desired end results may be achieved. For example, placing a grid like electrode between cathode and anode permits a small signal applied to said grid to greatly influence the flow of current from cathode to anode: this is the vacuum triode used for amplification. Operation of these devices depends upon the ability of the cathode to emit electrons into the vacuum.
Devices employing current flowing through a gas also require electrodes which easily emit electrons. Further, propulsion devices which operate on the principal of current flowing through diffuse plasmas in magnetic fields also depend heavily on the ability of electrodes to easily emit electrons.
Most such devices make use of the heated thermionic cathode. In such a cathode, a metal or oxide coated metal is heated until thermally excited electrons are capable of escaping from the metal. Such thermionic cathodes are capable of operation at current densities up to several hundreds of amperes per square centimeter. Such devices still find active use in high power devices such as are found in radio transmitters, however at the small scale the solid state transistor has virtually replaced the vacuum tube in all uses.
Vacuum Diode-Based Devices
In Edeleson's disclosure, filed Mar. 7, 1995, titled "Electrostatic Heat Pump Device and Method", Ser. No. 08/401,038, now abandoned two porous electrodes were separated by a porous insulating material to form an electrostatic heat pump. In said device, evaporation and ionization of a working fluid in an electric field provided the heat pumping capacity. The use of electrons as the working fluid is disclosed in that application. In my subsequent disclosure, filed Jul. 5, 1995, titled "Method and Apparatus for Vacuum Diode Heat Pump", Ser. No. 08/498,199, an improved device and method for the use of electrons as the working fluid in a heat pumping device is disclosed. In this invention, a vacuum diode is constructed using a low work function cathode.
In Edelson's further subsequent disclosure, filed Dec. 15, 1995, titled "Method and Apparatus for Improved Vacuum Diode Heat Pump", Ser. No. 08/573,074, issued as U.S. Pat. No. 5,699,668 the work function of the anode was specified as being lower than the work function of the cathode in order to optimize efficient operation.
In a yet further subsequent disclosure, filed Dec. 27, 1995, titled "Method and Apparatus for a Vacuum Diode Heat Pump With Thin Film Ablated Diamond Field Emission", Ser. No. 08/580,282, now abandoned, Cox and Edelson disclose an improvement to the Vacuum Diode Heat Pump, wherein a particular material and means of construction was disclosed to further improve upon previous methods and devices.
The Vacuum Diode at the heart of this Vacuum Diode Heat Pump may also be used as a thermionic generator: the differences between the two devices being in the operation of the diode, the types and quantities of external energy applied to it, and the provisions made for drawing off, in the instance of the thermionic converter, an electrical current, and in the instance of the Vacuum Diode Heat Pump, energy in the form of heat.
In Cox's disclosure, filed Mar. 6, 1996, titled "Method and Apparatus for a Vacuum Thermionic Converter with Thin Film Carbonaceous Field Emission", Ser. No. 08/610,599, now abandoned, a Vacuum Diode is constructed in which the electrodes of the Vacuum Diode are coated with a thin film of diamond-like carbonaceous material. A Vacuum Thermionic Converter is optimized for the most efficient generation of electricity by utilizing a cathode and anode of very low work function. The relationship of the work functions of cathode and anode are shown to be optimized when the cathode work function is the minimum value required to maintain current density saturation at the desired temperature, while the anode's work function is as low as possible, and in any case lower than the cathode's work function. When this relationship is obtained, the efficiency of the original device is improved.
Electrides and Alkalides
In Edelson's previous disclosure, entitled "Method and Apparatus for Vacuum Diode-Based Devices with Electride-Coated Electrodes", U.S. Pat. No. 5,675,972, incorporated herein by reference in its entirety, he describes Vacuum diode-based devices, including Vacuum Diode Heat Pumps and Vacuum Thermionic Generators, in which the electrodes are coated with an electride. These materials have low work functions, which means that contact potential difference between cathode and anode may be set against the effects of space charge, resulting in an improved device whereby anode and cathode may be set at a greater distance from each other than has been previously envisaged.
In a further disclosure filed Nov. 6, 1996, titled "Low Work Function Electrode", Ser. No. 08/744,574, issued as U.S. Pat. No. 5,910,980, incorporated herein by reference in its entirety, Edelson discloses a metal surface coated with a heterocyclic multidentate ligand compound, which reduces work-function and facilitates the emission of electrons.
In a further subsequent disclosure filed Sep. 22, 1997, titled "Low Work Function Electrode", Ser. No. 08/935,196, issued as U.S. Pat. No. 5,874,039 incorporated herein by reference in its entirety, Edelson discloses a substrate coated with a compound comprised of a cation complexed by a heterocyclic multidentate ligand, which provides a surface having a low work-function and facilitates the emission of electrons.
It has now been discovered that the thermionic emissive properties of electride materials are much improved following a molecular change to the crystal lattice structure of the electride.